Remove #pragma once from ash

ash/shell/window_watcher.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_SHELL_WINDOW_WATCHER_H_
 #define ASH_SHELL_WINDOW_WATCHER_H_
-#pragma once
 
 #include <map>
 
 #include "ash/launcher/launcher_types.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "ui/aura/window_observer.h"
 
 namespace aura {
 class Window;
@@ skipping 27 matching lines @@
   // Maps from window to the id we gave it.
   IDToWindow id_to_window_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowWatcher);
 };
 
 }  // namespace shell
 }  // namespace ash
 
 #endif  // ASH_SHELL_WINDOW_WATCHER_H_